Stringent regulations exist governing the operation of radio telephones, yet they are becoming a widely used consumer product. Accordingly their manufacture and servicing has become highly cost competitive.
In a mobile radio telephone there are many circuits whose resonance frequency, power level and the like have to be within certain critical limits. Thus if one mobile telephone in a cellular mobile telephone system is out of tune, this can interfere with others and its own performance will also suffer. Accordingly once the telephone circuit has been assembled it is then necessary to adjust the circuits using conventional trimming resistors, capacitors and the like. There are a large number of such trimming devices, typically 14 or more in a mobile telephone, and so this involves a great deal of manual input which significantly adds to the cost.
Attempts to reduce this manual trimming have involved the selection of high quality components for the circuits. However this involves more expensive components and is not a solution to maintaining the long term compliance of the mobile telephone with the regulations. Electronic components age with use and their properties change. It is therefore necessary for the mobile telephone to be serviced about once a year to ensure it still meets the regulations. Because mobile telephones are widely used consumer items, however, inexpensive servicing costs and speed of servicing are important objectives. But the large number of manually required adjustments with conventional mobile telephones has prevented the achievement of these desirable objectives and has discouraged owners from undertaking regular servicing.